Method of and apparatus for obtaining carbon dioxide



July 21, 1936.

- F. B. HUNT ET Al. 2,048,656

METHOD OF AND APPARATUS FOR OBTAINING CARBON DIOXIDE Fiied Nov. 1 8, 1931 CO Ladznsolmni 9- Pur C 2 Steam 1 Jwomtow Franklin 15'. Hunt arid- Raber L. Tamra;

Patented July 21, 1936 UNITED STATES METHOD OF AND APPARATUS FOR OBTAIN ING CARBON DIOXIDE Franklin B. Hunt and Robert L. Turner, Chicago,

Ill., assignors to The Liquid Carbonic Corporation, Chicago, 111., a corporation of Delaware Application November 18, 1931, Serial No. 575,779

16 Claims.

The present application relates to a method of and apparatus for obtaining carbon dioxide, and

more particularly to a method for obtaining :carbon dioxide which may be carried out by novel apparatus of extremely high efiiciency.

An object of the invention is to provide a 'method of and apparatus'for obtaining carbon dioxide without the use of massive apparatus. A further object of the invention is to provide a method of obtaining carbon dioxide in which the absorption of carbon dioxide from a gaseous mixture, and the removal of the carbon dioxide .from the absorbent medium are carried on at sub-zero temperatures. A further object of the invention is to provide a method of separating carbon dioxide from gaseous mixtures which involves the steps of absorbing the carbon dioxide in a'liquid medium having substantially no absorptivity for the other gases in the mixture, and then boiling the carbon dioxide out of the absorbent medium, using only atmospheric heat to effect such separation. Further objects of the invention will appear as the description proceeds.

To the accomplishment of the above and related objects, my invention may be embodied in the form illustrated in the accompanying drawing, attention being called to the fact, however, that the drawing is illustrative only, and that change may be made in the specific construction illustrated and described, or in the specific steps stated, so long as the scope of the appended claims is not violated.

The single figure is a diagrammatic illustration of a plant constructed in accordance with the present invention.

As illustrated, the plant comprises a furnace or combustion chamber ID with which is associated a boiler II for utilizing the heat of combustion. A conduit I2 is adapted to carry the gaseous products of combustion from the combustion chamber I to and through a scrubber |3 wherein the gaseous mixture is stripped of its solids. A conduit I4 conducts the scrubbed gases to a blower l5, whence the gases are forced through a pipe l6 to a coil IT. A conduit l8 leads from the coil I I to a contact chamber 2| Preferably, a refrigerating mechanism I 9 adapted to be driven by a steam engine 20, is associated with the conduit l8, said refrigerating mechanism being adapted to reduce the temperature of the gases in the conduit l8 to as low a'temperature as is commercially practicable.

The contact chamber 2| contains a suitable liquid of a character having a high degree of solubility for carbon dioxide at low temperatures,

the liquid medium having practically no solubility for the other components of the gaseous products of combustion. We have found that there are several substances having the requisite properties, some of these being ethyl alcohol, methyl alcohol, acetone, ether, ethyl acetate, and methyl acetate. Y

Of these, we now believe ethyl acetate to be the most satisfactory medium foruse in-the present process.

A conduit 22 leads from the contact chamber 2| to a coil 23, from which a conduit 24 leads to an atmospheric boiler 25. A conduit 26 is adapted to conduct gaseous carbon dioxide from the boiler 25 to a compressor 21 connected to be driven by a steam engine 28, a conduit 29 leading from the-compressor 21 either to another compressor or compressors, or to a receptacle for carbon dioxide.

A conduit 30 extends from the contact chamber 2| and into heat interchanging relation with the coil ll.

A conduit 3| is connected to the chamber- 2| and has associated therewith "a refrigerating mechanism 32 adapted to be driven by a steam engine 33. The conduit 3| is likewise connected with the boiler 25, and the portion of the conduit 3| between the boiler 25 and the refrigerating mechanism 22 is arranged in heat interchanging relation with the coil 23.

A steam line 34 is connected to the boiler II, and is provided with branches 35, 36, and 31 adapted, respectively, to supply steam to the engines 2|], 33, and 28.

It is to be understood that, while we have indicated separate steam engines for driving the refrigerating mechanisms Hi and 32 and the compressor 21, all of these mechanisms might be driven by a single steam engine. r v When operation of the system is to be initiated, a suitable supply of solvent is filled into the contact chamber 2| and the atmospheric boiler 25. The refrigerating mechanism 32 is then operated to reduce the'temperature of the solvent to a value somewhere between 59 and 78" C. In some instances, it may be necessary to provide a circulating pump in the circulating system including the chamber 2| and the boiler 25.

After the temperature of the solvent "in the chamber 2| has been reduced to a suitable value, the blower l and the refrigerating mechanism 9 are started, and flue gas from the furnace I0 is led through the scrubber l3 and the refrigerating mechanism l9 to the contact-chamber 2|.

At a temperature of 59 0., ethyl acetate will r of carbon dioxide.

absorb approximately 89 volumes of carbon dioxide. 'At a temperature of -78;C., thesame medium wili'absorb approximately 2'73, volumes The solution of carbon dioxide in the solvent liquid is led through the conduit 22, the coil 23, and the conduit 24 to the boiler 25. Therboiler 25 is not heatinsulated,

and atmospheric heat is permitted to raise the temperature of the solution in the boiler 25 to approximately C. at which temperature only approximately 32 volumes of carbon dioxide 5 will remain in the.solution.-,-= The carbon-dioxide driven out of the solution flows through V the conduit 26 to the compressor'2'l, and thence '15 through the conduit 29 either to further oompressors or to a storage receptacle. I 'In thechamber 2|, the'temperatureof the whole'volume of gaseous .mixture,is; of course,.'

reduced. The residual gases, not dissolved in the.

solvent medium, flow through the conduit 30 and,

sincea portion'fofsaid conduit 30; isas'sociated with-gcoil l1, theresidual gases absorb heat from the boiler 25 flows, at a. temperature..ofapproxi- Lmately +30? C.,through the conduit 31. Since a portionof said conduit 3 l adjacent the boiler .25

' isarfaiiged in heat interchanging relation with the coil 23' ini-which iscontained a solution at a temperature ranging. between '59 and 7 8 Cr, the solvent. in the'conduit 31, is cooled before, it i'eaches'the refrigerating mechanism 32,

land- 78C. ;It willzthusbezsee'n that, once the solvent has "been brought to a'working temperature, the re- 7 tofa--temperature ranging. between, -40? and -55 -C. "In the refrigerating mechanism'532,:the temperature of the. solvent in the conduit 3.l is further reduced-to a value ranging: between "-59? frigerating load-upon the system consists merely of: (a) Coolingthe pure'carbon dioxide to efi'ect',

liquefaction .ofsolidifiCation thereof, (b) "offsettingimperfect heatinterchange in the'coils l1 and, 23,and (a)? offsetting heatleakage. b

7 It will be noted thatfno'means' for effecting circulation of liquid between the chamber 2| and the: boiler 25 is illustrated; 'As has been stated,

:the solventiused has an extremely high solubility for carbon dioxide, dissolving from to 300 times its own volume of carbon dioxide,,depehding upon the temperatureused. This fact permits theme of the airlift principle ,to effect circulationj'qf the;solvent, andis expected toieliminate entirely the necessityforji expenditure of energy to; effect. the circulationtof the solvent.

A stillfurther advantage ,derived from the use I of "the present system lies in thefactthatthe solvents suggested" are of suchcharacter that their'solubility for carbon dioxide is substantial-'- ly unaifectedby'the pressure of the carbon dioxide "Forinstance, at a temperature of 59f"C.,

, a pressure variationpfrom; millimeters to- 600 millimeters 'efiect'savariationin solubility of only five volumes. At atemperatureof -78. 'C.., a 70.

"bility 'variation of only eighteniV01l1IIleS,IthiS' variation beingjapproximately 6% at either'tem corresponding pressure variation efiects' a soluperature; 1

r A still further advantage of the present system lies in. the fact that the; vapor pressures oftheva- -ume of the solvent medium. v

Atmospheric heat is' usedineffecting separat *rioussolvents is very low at the working temperatures, so that'the contamination of the carbon dioxide by vaporized solvent is exceeding slight. In'the well knownflye process of obtaining carbon dioxide, the vapor pressureof the water at the temperatures required to remove the carbon dioxide. from the absorbent is relatively high, so that it is necessary to provide a condenser. to.

separate the water vapor fromthe carbon di.

oxide. 7 b

'Because of the extremely high solubility for carbon dioxide of the various solvents here under consideration, thevolume ofs'olvent required for r I It thus becomes possible to use small sizeequipment. For instance,

the system is quite small.

a plant producing approximately 1000 pounds of 1 'tion of 10 to .15 gallons of ethyl acetate per minute, whereas a circulation" of 200 to 300 gal- "carbon dioxide per hour may use equipment of a V 7 size only largejenough to accomodate a circulalons' of'lye solution would be required tohandle the same amount of carbon dioxide.

The small size of the equipment required-pf course facilitates heat insulation ofthe equip- V ment- The energy required forcirculating thesolvent, even if the air lift principle be disregarded,isma terially reduced because of the reduction involtion of carbon dioxide from thesolvent,rso that none'of the energy generated by the combustion of the fuel is requiredtoaccomplish this separa:

tion;

The system is of such charaeten andsishso arranged, that'the combustion of the fuelinithe products of combustion; so that excess power is .availablefor liquefaction or solidification of the 7 carbon dioxide, or for other uses We claim as our invention:

5 1.;The process, of: separating carbondioxide from a gaseous mixture, which includes the steps of bringing the mixture into, contact, .under. a

furnace 10 generates more energy than .is' required to separate the'volume of carbon dioxide produced by such combustion from the other 7 .49

pressure not exceeding. atmospheric pressure,

consisting of ethyl alcohol,-methyl alcohol, acetone, ether, ethyl acetate, and methylacetate, removing 'undissolved gases from contact, with with a liquidv solvent consisting of one of agroup such liquid, and driving carbon dioxider rout of 7 solution in such liquid;

*2. The process of separating carbon' dioxide" froma gaseousfmixture, which consists inbringing the mixture into intimate contact at substantially atmospheric pressurewith-aliquid solvent consisting of 'one-ofja group consisting of: ethyl alcohoL methyl alcohol, acetone, ether, ethylacetate, and methyl acetate, whereby a, portion of the carbon'dioxide is dissolvedin'the solvent, re movingthe residual gases from contact with the solvent, and driving a portion of the*dissolved carbon dioxide out of solution' by heating,- the solvent being continuously held at sub-zero temperatures.

j;:j processiof separating carbon, dioxide froma gaseous mixture, which consists in bringing the mixture into intimate contactwith a liquid solvent consisting of one of a group consisting of ethyl alcohol, methyl alcohol, acetone,

ether, ethyl acetate, and methyl acetate,..at a temperature lower than -59 C., and at substantially atmospheric pressure, whereby' carbon dioxide is dissolved in the liquid while the other gases of. the mixture are notydissolved, drawing off the residual gases, permitting the temperature of the solution to rise, .under the influence of atmospheric heat, whereby a portion of the dissolved carbon dioxide is driven out of solution, and collecting the carbon dioxide so driven out of solution.

4.'The process of separating carbon dioxide :fromia' gaseous mixture whichincludes the steps of bringing the mixture into contact with acetone, removing undissolved gases from contact with. the. acetone, and driving carbon dioxide out of solution, by increasing the temperature of the removing undissolved gases from contact with the ether, and driving carbon dioxide out of solution, by increasing the temperature of the solution.

6. The process of separating carbon dioxide from a gaseous mixture which includes the steps of bringing the mixture into contact with ethyl acetate, removing undissolved gases from contact with the ethyl acetate, and driving carbon dioxide out of solution, by increasing the temperature of the solution.

7. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with acetone, whereby a portion of the carbon dioxide is dissolved in the acetone, removing the residual gases from contact with the acetone, and driving a portion of the dissolved carbon dioxide out of solution by heating, the acetone being continuously held at sub-zero temperature.

8. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with ether, whereby a portion of the carbon dioxide is dissolved in the ether, removing the residual gases from contact with the ether, and driving a portion of the dissolved carbon dioxide out of solution by heating, the ether being continuously held at sub-zero temperature.

9. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with ethyl acetate, whereby a portion of the carbon dioxide is dissolved in the ethyl acetate, removing the residual gases from contact with the ethyl acetate, and driving a portion of the dissolved carbon dioxide out of solution by heating, the ethyl acetate being continuously held at sub-zero temperature.

10. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with acetone at a temperature lower than minus 59 degrees C., whereby carbon dioxide is dissolved in the acetone while the other gases of the mixture are not dissolved, drawing off the residual gases, permitting the temperature of the solution to rise, under the influence of atmospheric heat, whereby a portion of the dissolved carbon dioxide is driven out of solution, and collecting the carbon dioxide so driven out of solution.

11. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with ether at a temperature lower than minus 59 degrees C., whereby carbon dioxide is dissolved in the ether while the other gases of the mixture are not dissolved, drawing off the residual gases, permitting thetemperature of the solution to rise, under the influence'of atmospheric heat, whereby a portion of the dissolved carbon dioxide is driven out of solution and collecting the carbon dioxide so driven out of solution.

12. The process of separating carbon dioxide from a gaseous mixture which consists in bringing the mixture into intimate contact with ethyl acetate at a temperature lower than minus 59 degrees C., whereby carbon dioxide is dissolved in chamber, a second conduit connecting said chamber with said boiler, a third conduit connecting said boiler with said chamber, and a fourth conduit leading from said chamber, portions of said second and third conduits being arranged in heat-exchanging relation with each other, and

portions of said first and fourth conduits being arranged in heat-exchanging relation with each other.

14. Apparatus for separating carbon dioxide from gaseous mixtures, comprising a source of gaseous mixture containing carbon dioxide, a contact chamber, a boiler, said chamber and said boiler containing a liquid solvent for carbon dioxide, a conduit connecting said source with said chamber, a second conduit connecting said chamber with said boiler, a third conduit connecting said boiler with said chamber, a fourth conduit leading from said chamber, refrigerating means associated with said first conduit, and refrigerating means associated with said third conduit, a portion of said second conduit being arranged in heat-exchanging relation with a portion of said third conduit between said boiler and said refrigerating means associated with said third conduit, and a portion of said fourth conduit being arranged in heat-exchanging relation with a portion of said first conduit between said source and said refrigerating means associated with said first conduit.

15. Apparatus for obtaining carbon dioxide, comprising a fuel combustion chamber, a steam boiler associated with said combustion chamber, a contact chamber, an atmospheric boiler, said contact chamber and atmospheric boiler containing a solvent for carbon dioxide liquid at subzero temperatures, a conduit for conducting products of combustion from said combustion chamber to said contact chamber, a second conduit for conducting solvent from said atmospheric boiler to said contact chamber, refrigerating mechanism associated with said second conduit and adapted to reduce the temperature of fluid in said second conduit to sub-atmospheric Values, means operable by steam generated in said first-named boiler for driving said refrigerating mechanism, a conduit for conducting solution from said contact chamber to said atmospheric boiler, and a conduit for conducting carbon dioxide from said atmospheric boiler.

16. Apparatus for obtaining carbon dioxide,

conipfisihg :a'fuemonibusmn 'han'xb'er, d stea2m boiler associated with said jcombustionjchambr, =a; contact hamb'er an *atmospheric boiler, said contact chamber and atmospheric boilr containing 'a solvren t for carboii dioxide-liquidit sub zero temperatures, a conduit 7 for conducting 7 products of "combustion f rQm -Sai'd combustion 7 fig "chamber to said contact "chambe' -a'second' conduit for conducting solvent fromsaid atmo'si pheric "boiler -':to "said' cont'ajct chamber, refri'gr ating mechanism associate'd with' said sec'on'd --cbnduit and adapted 'to fedfice the temperature itingmecha'nism, a. conduit fo'ricqnductlng' 'solution'l'rom said contactbhhmber w slald' atms .-pheric*boi1er, '-a. "compressor. 'connecteq "1,10 s'ai'd atmospheric boiler and adapted 'td receive the liberated carbon dioxide therefrom, "and means op'erable by steamigenerated" 1n" Said first-timed boi'ler for driving said compressor.

V FRANKLIN'B;

"ROBERT L.

r fo V 

